Inductors have always been one of the basic components of electrical circuitry and are still commonly used even with current generations of microprocessors. There is a great advantage when designing microprocessors and other circuitry to be able to choose an inductor having desirable characteristics from a catalog of inductors having different values for a number of different parameters. For example, in designing current switch mode power supplies, there are three major components, inductors, storage capacitors and power MOSFETs (Metal Oxide Semiconductor Field Effect Transistors). By utilizing high performance inductors having specific values of parameters, it may be possible to use a less expensive MOSFET or a MOSFET that switches at a lower frequency. Alternatively, a smaller power supply overall may be produced or a power supply that uses less power and generates less heat. It may also allow fewer phases in the power supply design due to a high performance inductor.
However, in order to have inductors with these different performance values, it is often necessary to either vary the cross section of the wire used in the inductor or to vary the shape of the coil within the inductor. In addition, in changing the shape of the coil, it is possible to minimize the wasted space inside the inductor body and to optimize current handling capabilities and EMI (Electro Magnetic Interference) characteristics.
The predominant method of forming an inductor currently is to use enamel coated copper wire formed into a round coil shape. This coil may be placed in magnetically permeable powder material which is then compressed into a block or may be placed in a preformed two piece case made of similar magnetically permeable material. It is necessary to have an enamel coating on the wire because the coil comes into contact with itself. Currently, the most popular shape is a round shaped coil which leaves wasted space when placed in a square package. Another alternative is to wrap enamel coated wire around a donut shaped core made from magnetically permeable material.
These and other currently available methods of making inductors are not completely satisfactory. Forming shaped coils other than round or donut shaped is more difficult. Also, the use of other than round cross-sectional shaped wires is not convenient. Thus, it is difficult to obtain a coil having unusual characteristics because of the limitations on the shape of the coil and the wire.
A method of making jewelry and other cast metal pieces known as the “lost wax method” has been known for perhaps over 5,000 years. This method utilizes the formation of the desired object first in a soft material such as wax. A material such as plaster is then cast around the wax model and allowed to dry. The entire object is heated so as to melt the wax but not harm the plaster surrounding it. The wax is allowed to run off leaving a hole in the mold in the same shape of the original wax object. Metal is then poured in this opening to form the desired object in the same shape as the original wax form. Since the original wax material is easier to work, it allows the jeweler to form complex shapes relatively easily. Once the metal object is cooled, the plaster cast is removed and the final metal object is polished and otherwise finished to form the finished jewelry object. While this method has been used to make many devices, it has not been utilized for electronic devices such as electronic inductors.